解决方法
SEL selector = NSSelectorFromString(@"applySketchFilter:");
IMP imp = [FWApplyFilter methodForSelector:selector];
UIImage* (*func)(id, SEL, UIImage*) = (void *)imp;
UIImage *image = func([FWApplyFilter class], selector, self.currentImage);
SEL selector = NSSelectorFromString(@"applySketchFilter:");
IMP imp = [FWApplyFilter methodForSelector:selector];
UIImage* (*func)(id, SEL, UIImage*) = (void *)imp;
UIImage *image = func([FWApplyFilter class], selector, self.currentImage);